1. Field of the Invention
The present invention relates to an integration rod of a projection optical system, and more particular to a device for fastening/adjusting the position of the integration rod when the integration rod is oblique.
2. Description of the Prior Art
In the prior art, the projection optical system comprises an integration rod to homogenize the light passing through it. Afterward, the light being homogenized is shone on a light valve after passing through the integration rod, so that the brightness of the image projected on a display screen is uniform. Once the integration rod becomes oblique during the process of manufacture or assembly, the light cannot fully pass through the integration rod. Accordingly, the light that cannot pass through the integration rod is lost, such that the brightness of the projected image decreases. Therefore, the position of the integration rod should be adjusted after being assembled.
Referring to FIG. 1, FIG. 1 is a schematic diagram of a projection optical system 10, an integration rod 12, and a fastening/adjusting device 14 of the prior art. The device 14 is used for fastening the integration rod 12 onto an inner wall 16 of a housing 11 of the projection optical system 10. The device 14 is also used for adjusting a horizontal position and a vertical position of the integration rod 12 relative to the inner wall 16 of the projection optical system 10. The device 14 comprises a plate spring 15 and two adjusting screws 14a and 14b. The plate spring 15 is monolithically formed with the device 14, and a top surface and a side surface of the plate spring have a metal spring piece 15a and 15b respectively. The adjusting screw 14a corresponding to the metal spring piece 15a is used for adjusting the vertical position of the integration rod 12. The adjusting screw 14b corresponding to the metal spring piece 15b is used for adjusting the horizontal position of the integration rod 12.
As shown in FIG. 1, because the two adjusting screws 14a and 14b both directly adjust the integration rod 12, one of the adjusting screws influences the other when adjusting the integration rod 12. After the device 14 has been used for a span of time, the outer frame of the integration rod 12 is damaged. When one of the two adjusting screws 14a and 14b sinks into the outer frame of the integration rod 12 and cannot adjust the position of the integration rod 12, the other one is influenced and no longer able to adjust the position of the integration rod 12. Moreover, the device 14 of the prior art utilizes the metal spring pieces 15a and 15b to adjust and restore the position of the projection optical system 12. In general, the restoring force of the metal spring piece is not strong and is often not enough for practical use. Furthermore, the outer frame of the integration rod 12 of the prior art directly contacts the inner wall 16 of the housing 11. When the position of the integration rod 12 is adjusted, there is friction between the integration rod 12 and the inner wall 16, and consequently the adjusted direction is oblique.
Therefore, the present invention provides a device for fastening/adjusting the position of an integration rod of a projection optical system to solve the above problems.